The following question emerged from a conversation with the machine learning theorist Pedro Domingos a month ago.
Consider a hypothetical race of intelligent beings, the Armchairians, who never take any actions: never intervene in the world, never do controlled experiments, never try to build anything and see if it works. The sole goal of the Armchairians is to observe the world around them and, crucially, to make accurate predictions about what’s going to happen next. Would the Armchairians ever develop the notion of cause and effect? Or would they be satisfied with the notion of statistical correlation? Or is the question kind of silly, the answer depending entirely on what we mean by “developing the notion of cause and effect”? Feel free to opine away in the comments section.